Assessing the Distribution Characteristics of Surface Water Geochemistry and Pollution of Heavy Metals within Soil in the Changjiang River Delta, China

This study aimed to understand the spatial distribution and geochemical characteristics of heavy metals in soil in Changjiang River Delta, and also the impact of surface water geochemistry on the mobility of heavy metals in soil. The levels of Ca2+ and Na+ in surface water reached 80% of total cation level, ranging 33.00-97.50 mg/L and 9.00-334.90 mg/L, respectively. HCO3- was more than 50% of total anion concentration, making the type of surface water as Ca-HCO3 or Ca-Na-HCO3. The concentration of cations and anions followed the order: coastal > middle > inland. The soils were strongly polluted with Cd in this study. More than 50% of Cd concentration exceeded the standard. Spatial changes in As, Cd, and Pb levels followed the order: middle > coastal > inland, same as that for soil pH. Speciation results of heavy metals showed that more than 50% of Cd was exchangeable. Principal component analysis results showed that the change in exchangeable fraction of As, Hg, and Pb followed the same order: middle > coastal > inland. Exchangeable Cd followed a trend different from that of Cr. Three areas were characterized by the mobility of As, Hg, and Pb. Scores of samples from different areas implied the influence of surface water on the mobility of heavy metals in soil. Geochemical variation in surface water indicated the mobility of heavy metals through correlation and spatial analysis of geochemistry of surface water and speciation of heavy metals in soil.